PET film has excellent productivity, mechanical strength and dimensional stability, however, a strong curling habit remains after development to give rise to poor handle-ability and therefore, the use thereof is restricted in spite of the above-described excellent properties. Namely, it has been difficult to use the PET film as a rolled film such as a color negative film.
Recently, the photographic material has been used in diversified fields and it is radically driven to achieve miniaturization of a camera, high-speed film conveyance in photographing and high magnification in taking a picture. In association therewith, the support is required to have strength, dimensional stability and thin film capability. Further, as the miniaturization of a camera proceeds, miniaturization of a patrone has been increasingly demanded. In order to realize the miniaturization of a patrone, two problems remain to be solved. One problem is the reduction in mechanical strength accompanying the thinning of film and another problem is an intensified curling habit generated after storage due to the miniaturized spool.
As a method for reducing the curling habit of polyester film, methods as described, for example, in JP-A-51-16358 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-1-131550 and U.S. Pat. No. 4,141,735 are known. However, the silver halide photographic material is used in various environment, for example, it may be left in an automobile parked outdoors in midsummer, where the temperature temporarily rises up near 90.degree. C., and accordingly, it has also been demanded to prevent intensification of the curling habit at such high temperatures.
The high magnification of a print can first be achieved when not only the light-sensitive layer is uniformly coated but also a uniform undercoat layer free from aggregate is realized.
Heretofore, the binder used for the undercoat layer has been mainly gelatin. However, when an organic solvent capable of drying the undercoat layer at a low temperature within a short period of time is used, the gelatin containing a large amount of metals or ions readily aggregates. The aggregate has been conventionally removed by filtering the undercoating solution through a filter after the preparation of the solution, however, if the filter size is made small, although the aggregate as a problem in printing may be removed, the frequency of filter exchange increases, which is disadvantageous in view of productivity.
Further, an attempt has been made to improve coat-ability of the undercoating solution by adding a surface active agent to the undercoating solution. However, the anionic surface active agent exhibits poor solubility in the coating solution containing an organic solvent to fail in imparting sufficient surface activation effect, whereas if a cationic surface active agent is used as a surface active agent for the undercoating solution, aggregation is generated at the interface of the undercoat layer on coating of an emulsion layer containing a large amount of anionic materials to deteriorate the surface property. Furthermore, when a solution having dispersed therein as an electrically conductive material fine particles of at least one crystalline metal oxide selected from the group consisting of ZnO, TiO.sub.2, SnO.sub.2, Al.sub.2 O.sub.3, In.sub.2 O.sub.3, SiO.sub.2, MgO, BaO, MoO.sub.3 and V.sub.2 O.sub.5, which are used as an antistatic agent, or a composite oxide of these is coated on the undercoat layer, aggregation is generated at the interface of the undercoat layer because the electrically conductive material is negatively charged in the coating solution. Still further, with the use of a betaine surface active agent, aggregation is caused at the interface on coating an emulsion layer containing a large amount of anionic materials. Thus, the addition of a surface active agent is not preferred.
In order to bond a silver halide emulsion layer to a polyester support, an undercoat layer must be provided. For coating an undercoat layer of a polyethylene terephthalate support, methods described in JP-A-48-24723, JP-B-49-26580 (the term "JP-B" as used herein means an "examined Japanese patent publication"), JP-A-51-114120, JP-A-1-210947 and JP-A-3-109545 may be used. However, the polyester support of the present invention is difficult to adhere as compared with the polyethylene terephthalate film and conventional techniques fail in adhesion of the polyester support. Further, as the environment where the silver halide photographic material is used is diversified, the adhesion performance becomes worse in coating an emulsion layer on the polyester support according to conventional techniques and a further improved technique has been demanded. Furthermore, in the case where a polyester support is used, the polyester support is liable to have electric charge during conveyance at photographing or in an automatic developing machine and as a result, a discharge occurs to cause fogging. The current techniques for preventing electrification are insufficient because there arises a problem that since materials used are eluted out into the processing solution, the electrification preventing performance (i.e., the antistatic property) is lost after development, and dusts attached due to the electric charge are also printed.
JP-A-51-3619 describes the use of polyamide resin in the undercoat layer so as to bond a silver halide emulsion layer to the polyester support.
One of the surface treatment techniques for bonding a silver halide emulsion layer to the polyester support is glow discharge treatment. U.S. Pat. Nos. 3,462,335, 3,761,299 and 4,072,769 and British Patent 891,469 describes on the glow discharge treatment. However, the methods described therein cannot provide adhesion sufficiently strong to be retained in a dry condition and in a processing solution. Further, specific gas such as inert gas, a nitrogen oxide or organic compound gas must be introduced but this is not preferred either in view of cost or environmental conservation. JP-A-59-556430 describes a method where the gas composition in the discharge atmosphere is restricted to gases generated in the container resulting from that, in applying glow discharge treatment to the polymer surface, the polyester support itself is subjected to discharge treatment after the initiation of discharging, however, since the gas composition in the discharge atmosphere varies depending on the width of the polyester support, the conveyance speed or the support temperature at the surface treatment, a stable and adequate adhesive force cannot be obtained. JP-B-60-16614 describes a method where a vacuum glow discharge treatment is conducted at the surface temperature of polyester film of from 80.degree. to 180.degree. C., however, when the polyester support has a glass transition temperature of from 90.degree. to 200.degree. C., a satisfactory adhesive force cannot be obtained by the discharge treatment at a temperature higher than the glass transition temperature of the support.